Weidmüller PV DC COMBINER BOX, Operating Instructions Manual

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23 4000001903/00/04.2020
Connection of the communications (optional)
Please regard the following aspects when wiring the
RS485:
– The RS485 bus topology must be a daisy chain (see
picture below).
– Short stubs inside the combiner box should be at maxi-
mum 2 meters long.
– We recommend a bus length of 500 meters at maxi-
mum, even though the RS485 standard allows up to
1200 meters at low bit rates (i.e. 9600 bps and 19200
bps).
– Each end of the bus requires a 120 Ω 10 % ½ W ter -
mination resistor between D+ and D– (see the RS485
wiring diagram). One end of the bus will be the RS485
master which may or may not include an internal termi-
nation option. The other end will be inside the combiner
box farthest away from the master in terms of RS485
cable distance.
– This equipment loads the RS485 bus with 1/8 UL (Unit
Load).
– It is recommended not to mix Transclinic and other
RS485 slaves within the same bus.
– The D+ and D– of each Transclinic should use one
twisted pair of the cable, leaving the remaining wire (in
cables with 1.5 pairs) or the remaining twisted pair (in
cables with 2 pairs) for the C connection.
– Always make sure that D+, D– and C use the right
color-coded wire of the cable. It is a must to connect the
C pin of all the Transclinic and the RS– 485 master to-
gether (see picture below).
Transclinic
(RS-485 slave)
' ' &
Transclinic
(RS-485 slave)
' ' &
RS-485
master
' '
Transclinic
(RS-485 slave)
' ' & &
Figure 6.2 RS485 wiring diagram (daisy chain bus topology)
Damages to the RS485 transceiver IC of this
equipment due to the following wiring errors will
not be covered under warranty:
– Connecting the C pin of this equipment to
protective earth anywhere except in one point
(at the master end). This connection may be
already done internally inside the RS485 mas-
ter.
– Connecting the C pin of this equipment to the
cable shield inside a combiner box.
– Using non-twisted pair or non-shielded cables.
– Connect RS485 cables in a different way than
the specified in the wiring diagram of this user
manual.